| /* |
| * Copyright (C) 2010 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package java.util.regex; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| /** |
| * Used to make {@code String.split} fast (and to help {@code Pattern.split} too). |
| * @hide |
| */ |
| public class Splitter { |
| // The RI allows regular expressions beginning with ] or }, but that's probably a bug. |
| private static final String METACHARACTERS = "\\?*+[](){}^$.|"; |
| |
| private Splitter() { |
| } |
| |
| /** |
| * Returns a result equivalent to {@code s.split(separator, limit)} if it's able |
| * to compute it more cheaply than ICU, or null if the caller should fall back to |
| * using ICU. |
| */ |
| public static String[] fastSplit(String re, String input, int limit) { |
| // Can we do it cheaply? |
| int len = re.length(); |
| if (len == 0) { |
| return null; |
| } |
| char ch = re.charAt(0); |
| if (len == 1 && METACHARACTERS.indexOf(ch) == -1) { |
| // We're looking for a single non-metacharacter. Easy. |
| } else if (len == 2 && ch == '\\') { |
| // We're looking for a quoted character. |
| // Quoted metacharacters are effectively single non-metacharacters. |
| ch = re.charAt(1); |
| if (METACHARACTERS.indexOf(ch) == -1) { |
| return null; |
| } |
| } else { |
| return null; |
| } |
| |
| // We can do this cheaply... |
| |
| // Unlike Perl, which considers the result of splitting the empty string to be the empty |
| // array, Java returns an array containing the empty string. |
| if (input.isEmpty()) { |
| return new String[] { "" }; |
| } |
| |
| // Collect text preceding each occurrence of the separator, while there's enough space. |
| ArrayList<String> list = new ArrayList<String>(); |
| int maxSize = limit <= 0 ? Integer.MAX_VALUE : limit; |
| int begin = 0; |
| int end; |
| while ((end = input.indexOf(ch, begin)) != -1 && list.size() + 1 < maxSize) { |
| list.add(input.substring(begin, end)); |
| begin = end + 1; |
| } |
| return finishSplit(list, input, begin, maxSize, limit); |
| } |
| |
| public static String[] split(Pattern pattern, String re, String input, int limit) { |
| String[] fastResult = fastSplit(re, input, limit); |
| if (fastResult != null) { |
| return fastResult; |
| } |
| |
| // Unlike Perl, which considers the result of splitting the empty string to be the empty |
| // array, Java returns an array containing the empty string. |
| if (input.isEmpty()) { |
| return new String[] { "" }; |
| } |
| |
| // Collect text preceding each occurrence of the separator, while there's enough space. |
| ArrayList<String> list = new ArrayList<String>(); |
| int maxSize = limit <= 0 ? Integer.MAX_VALUE : limit; |
| Matcher matcher = new Matcher(pattern, input); |
| int begin = 0; |
| while (matcher.find() && list.size() + 1 < maxSize) { |
| list.add(input.substring(begin, matcher.start())); |
| begin = matcher.end(); |
| } |
| return finishSplit(list, input, begin, maxSize, limit); |
| } |
| |
| private static String[] finishSplit(List<String> list, String input, int begin, int maxSize, int limit) { |
| // Add trailing text. |
| if (begin < input.length()) { |
| list.add(input.substring(begin)); |
| } else if (limit != 0) { // No point adding the empty string if limit == 0, just to remove it below. |
| list.add(""); |
| } |
| // Remove all trailing empty matches in the limit == 0 case. |
| if (limit == 0) { |
| int i = list.size() - 1; |
| while (i >= 0 && list.get(i).isEmpty()) { |
| list.remove(i); |
| i--; |
| } |
| } |
| // Convert to an array. |
| return list.toArray(new String[list.size()]); |
| } |
| } |